Process for the preparation of dispersions using viscosity-increase inhibitors of water-soluble polymers

Abstract

A process for producing a water-soluble polymer dispersion comprising polymerizing water-soluble monomers having double bonds in an aqueous salt solution that dissolves the monomers but does not dissolve the formed polymer while stirring in the presence of a dispersant composed of a polymer electrolyte soluble in this aqueous salt solution to obtain fine polymer particles dispersed in the aqueous salt solution, characterized by adding at least one viscosity-increase suppressor selected from the group consisting of: (A) a polyvalent carboxylic acid or a salt thereof, (B) a polyvalent phenol, (C) a cyclic compound containing a hydroxyl group and a carboxyl group or a salt thereof, (D) gluconic acid or a salt thereof, (E) a reaction product obtained by reacting methoxyhydroquinone and/or (meth)acrylic cationic monomer with a compound that generates radicals in an oxidizing atmosphere, (F) a reaction product obtained by reacting (meth)acrylic cationic polymer with a compound that generates radicals in an oxidizing atmosphere, (G) a reaction product obtained by reacting (meth)acrylic cationic polymer with an oxidant, and a mixture thereof.

What is claimed is:  
     
       1. A process for producing a water-soluble polymer dispersion comprising polymerizing water-soluble monomers having double bonds in an aqueous salt solution that dissolves the monomers but does not dissolve the formed polymer while stirring in the presence of a dispersant composed of a polymer electrolyte soluble in said aqueous salt solution to obtain fine polymer particles dispersed in the aqueous salt solution, characterized by adding to the polymerization at least one viscosity-increase suppressor selected from the group consisting of: 
       (A) a polyvalent carboxylic acid or a salt thereof,  
       (B) a polyvalent phenol,  
       (C) a cyclic compound containing a hydroxyl group and a carboxyl group or a salt thereof,  
       (D) gluconic acid or a salt thereof,  
       (E) a reaction product obtained by reacting methoxyhydroquinone and/or (meth)acrylic cationic monomer with a compound that generates radicals in an oxidizing atmosphere,  
       (F) a reaction product obtained by reacting (meth)acrylic cationic polymer with a compound that generates radicals in an oxidizing atmosphere,  
       (G) a reaction product obtained by reacting (meth)acrylic cationic polymer with an oxidant, and a mixture thereof.  
     
     
       2. The process for producing a water-soluble polymer dispersion s set forth in claim  1 , wherein the water-soluble monomers having double bonds are composed of 0-30 mol % acrylic acid, 0-100 mol % acrylamide and 0-100 mol % cationic monomer represented by the following formula 1 and/or the following formula 2:                    
       (wherein, A represents O or NH, B represents C 2 H 4 , C 3 H 6  or C 3 H 3 OH, R 1  represents H or CH 3 , R 2  and R 3  represent an alkyl group having 1-4 carbon atoms, R 4  represents hydrogen, an alkyl group having 1-4 carbon atoms or benzyl group, and X −  represents a counter ion);                    
       (wherein, A represents O or NH, B represents C 2 H 4 , C 3 H 6  or C 3 H 5 OH, R 5 , R 6 , R 7  and R 8  represent H or CH 3 , and X −  represents a counter ion).  
     
     
       3. The process for producing a water-soluble polymer dispersion as set forth in claim  1 , wherein said dispersant is a cationic polymer electrolyte in which 50-100 mol % of at least one type of cationic monomer selected from the group consisting of dimethylaminoethyl(meth)acrylate salt, dimethylaminopropyl(meth)acrylamide salt, di(meth)allylamine salt, (meth)acryloyloxyethyltrimethylammonium chloride, (meth)acrylamidopropyltrimethylammonium chloride, dimethyldiallylammonium chloride and a mixture thereof, and 50-0 mol % acrylamide are polymerized. 
     
     
       4. The process for producing a water-soluble polymer dispersion as set forth in claim  1 , wherein the salt that forms the aqueous salt solution is a bivalent anionic salt. 
     
     
       5. The process for producing a water-soluble polymer dispersion as set forth in claim  1 , wherein the (A) polyvalent carboxylic acid or the salt thereof is one selected from oxalic acid, adipic acid, tartaric acid, malic acid, phthalic acid and salts thereof. 
     
     
       6. The process for producing a water-soluble polymer dispersion as set forth in claim  1 , wherein the (B) polyvalent phenol is resorcinol or pyrogallol. 
     
     
       7. The process for producing a water-soluble polymer dispersion as set forth in claim  1 , wherein the (C) cyclic compounds having a hydroxyl group and a carboxyl group is one selected from m-hydroxybenzoic acid, p-hydroxybenzoic acid, salicylic acid, gallic acid, tannic acid and salts thereof. 
     
     
       8. The process for producing a water-soluble polymer dispersion as set forth in claim  1 , wherein the viscosity-increase suppressor (E) is obtained by reacting a compound that generates radicals in an oxidizing atmosphere in a solution containing methoxyhydroquinone and/or (meth)acrylic cationic monomer. 
     
     
       9. The process for producing a water-soluble polymer dispersion as set forth in claim  1 , wherein the total added amount of the viscosity-increase suppressors represented by (A) through (G) above is from 10 ppm to 10,000 ppm relative to the weight of the reaction solution. 
     
     
       10. The process of producing a water-soluble polymer dispersion as set forth in claim  1 , wherein the viscosity-increase suppressor is the member of the group which is a reaction product obtained by reacting (meth)acrylic cationic polymer with a compound that generates radicals in an oxidizing atmosphere. 
     
     
       11. The process of producing a water-soluble polymer dispersion as set forth in claim  1 , wherein the viscosity-increase suppressor is the member of the group which is a reactoin product obtained by reacting (meth)acrylic cationic polymer with an oxidant.